boxofbits Posted January 9, 2022 Report Share Posted January 9, 2022 Afternoon all Just in the process of re-fitting the gearbox in my 4a, and found that the threads on the rear rubber mounting must be an odd size? I thought they were 3/8”, but 3/8” or 7/16” UNF/UNC or don’t fit. Could they be BSF or BSW ? I cannot locate the original nuts. Thanks Kevin Quote Link to post Share on other sites
John Morrison Posted January 9, 2022 Report Share Posted January 9, 2022 Not an odd size Kevin, have you bashed them on removal? John. Quote Link to post Share on other sites
boxofbits Posted January 9, 2022 Author Report Share Posted January 9, 2022 42 minutes ago, John Morrison said: Not an odd size Kevin, have you bashed them on removal? John. Not to my knowledge John. I thought they would’ve been 3/8” UNF but a nut does not want to start by hand on either of the two studs. Don’t think they are UNC either. A 7/16” nut just about sleeves over the thread. Funnily enough, the parts manual shows the nuts complete with the mounting and not shown separately. Obviously the studs are moulded into the mounting, so what thread/pitch they used I’m not sure. Kevin Quote Link to post Share on other sites
John Morrison Posted January 9, 2022 Report Share Posted January 9, 2022 Kevin, just checked a stock one, certainly 7/16 UNF. Just a tip as well, I found cutting these two studs until just long enough, greatly helped sliding a replacement into place, when just changing the mount. John. Quote Link to post Share on other sites
Z320 Posted January 9, 2022 Report Share Posted January 9, 2022 (edited) If you want to have it easier next time to change it, cut out the rear bending (down) of the crossmember, than you can slide the mount with the crossmember on it out to the front. That‘s what an earlier owner did on my TR4A and this it what made it real easy for me. The photo is from another one of my posts. Ciao, Marco Edited January 9, 2022 by Z320 Quote Link to post Share on other sites
boxofbits Posted January 9, 2022 Author Report Share Posted January 9, 2022 (edited) 3 hours ago, John Morrison said: Kevin, just checked a stock one, certainly 7/16 UNF. Just a tip as well, I found cutting these two studs until just long enough, greatly helped sliding a replacement into place, when just changing the mount. John. Thanks John you are indeed correct and this plate from Revington confirms it is 7/16”. I’ve just measured a 7/16” UNF bolt which is 0.4375”. I’ve just got under the car and measured both studs and they come out at 0.3825”. The threads don’t look badly worn or stripped, and as said if I’d had 7/16” UNF nuts before they wouldn’t have been there as they’d have fallen off. Both studs are the same. Weird! https://www.revingtontr.com/tr4a/triumph-catalogue/p I’m wondering if this is an original Triumph OEM mounting, as I know it’s about 25 years old. In the original (paper version) triumph manual interestingly it doesn’t show or quote the nut or stud size, or available as separate items. Have the stud thread sizes been changed I wonder to 7/16” UNF on the new reproductions? Thanks Marco for the mounting mod info and pics. Life ain’t easy dealing with installation of these boxes! Sorry picture upside down. Edited January 9, 2022 by boxofbits Quote Link to post Share on other sites
RobH Posted January 9, 2022 Report Share Posted January 9, 2022 0.3825" is just over 9.7mm so could these be over-cut M10s? Quote Link to post Share on other sites
Z320 Posted January 9, 2022 Report Share Posted January 9, 2022 For a fast and easy change of the mount the bolt right side of the gearbox to the mount is @)=!!&%@ annoying! The one which goes through the gearbox flange and holds the exhaust bracket from below. The hex head (on top) is out of reach for a spanner - and the lower nut you can't move because is is welded on the exhaust bracket! Who had this idea, please? I had to cut the gearbox cover out to reach the nut. Ciao, Marco Quote Link to post Share on other sites
BlueTR3A-5EKT Posted January 9, 2022 Report Share Posted January 9, 2022 (edited) M10 I suspect. Have a memory of cursing the nuts on brother’s gearbox mount when my readily to hand unf socket did not fit. The mount we were fitting was new and had nuts supplied, (that is a give away in itself that it is not standard) so I suspect that repro has gone metric. Edited January 9, 2022 by BlueTR3A-5EKT Quote Link to post Share on other sites
boxofbits Posted January 9, 2022 Author Report Share Posted January 9, 2022 (edited) Thanks John and Marco for all the info and tips. I strongly suspect Rob and then Peter must be right. Tomorrow I’ll try an M10 nut on it. Tbh, the thread does look a bit metric? I can’t believe both studs would have worn or corroded that much to make the UNF nuts fall off! I was cursing also. There was a blue haze under my car for a while! Question which I don’t know the answer to, did Triumph, with the late TR6’s etc ever use metric threads as I assume the mounting is the same on the TR6? Fords were using metric on the Mk3 Cortina I believe right back in 1971. The mounting on my car was probably bought in the Cox and Buckles days, so maybe the manufacturer just embedded metric bolts in the mounting? It’ll be interesting to find out. Kevin Edited January 9, 2022 by boxofbits Quote Link to post Share on other sites
Ralph Whitaker Posted January 10, 2022 Report Share Posted January 10, 2022 I think the brake calipers changed to metric on later TR6s, so could be that the gearbox mount changed too. Ralph Quote Link to post Share on other sites
boxofbits Posted January 10, 2022 Author Report Share Posted January 10, 2022 They did indeed turn out to be M10’s. I guess the manufacturer used whatever was available to them at the time. Problem solved and thanks to everyone for the helpful comments. Kevin Quote Link to post Share on other sites
stuart Posted January 11, 2022 Report Share Posted January 11, 2022 12 hours ago, boxofbits said: They did indeed turn out to be M10’s. I guess the manufacturer used whatever was available to them at the time. Problem solved and thanks to everyone for the helpful comments. Kevin Lock washers? Also required on the outer plate mounting bolts too. Stuart. Quote Link to post Share on other sites
boxofbits Posted January 11, 2022 Author Report Share Posted January 11, 2022 52 minutes ago, stuart said: Lock washers? Also required on the outer plate mounting bolts too. Stuart. Thanks Stuart. I had a flat and spring on there before I think . I only crawled under it last night and screwed them on a few threads just to check they were metric, so hopefully I’ll get a chance to finish it this weekend. Regards Kevin Quote Link to post Share on other sites
RobH Posted January 11, 2022 Report Share Posted January 11, 2022 (Thread drift so apologies) I know it is conventional to use helical spring lock-washers and they are widely present on TRs but just to throw in a 'wobbly', don't expect them to actually lock anything. NASA in their fastener design manual say: “The typical helical spring washer … serves as a spring while the bolt is being tightened. However, the washer is normally flat by the time the bolt is fully torqued. At this time it is equivalent to a solid flat washer, and its locking ability is nonexistent. In summary, a lockwasher of this type is useless for locking.” https://ntrs.nasa.gov/api/citations/19900009424/downloads/19900009424.pdf There are a number of youtube videos which illustrate this point (helical spring at 2:43 here). Quote Link to post Share on other sites
boxofbits Posted January 11, 2022 Author Report Share Posted January 11, 2022 8 minutes ago, RobH said: (Thread drift so apologies) I know it is conventional to use helical spring lock-washers and they are widely present on TRs but just to throw in a 'wobbly', don't expect them to actually lock anything. NASA in their fastener design manual say: “The typical helical spring washer … serves as a spring while the bolt is being tightened. However, the washer is normally flat by the time the bolt is fully torqued. At this time it is equivalent to a solid flat washer, and its locking ability is nonexistent. In summary, a lockwasher of this type is useless for locking.” https://ntrs.nasa.gov/api/citations/19900009424/downloads/19900009424.pdf There are a number of youtube videos which illustrate this point (helical spring at 2:43 here). Thread drift? ..yeah nice one Rob ! I’d argue that a spring washer might exert a few ounces of clamping force even when flattened as it will distort to some extent. A shakeproof has small teeth as you know but once flattened might not even exert any pressure at all. I’ve not known many spring washers to fail in practice though. My car would be in bits all over the driveway by now if that was the case! The person doing the tightening didn’t seem to be putting much elbow into it, and did I see a dodgy cheapo Halfords socket being used? Not surprised it came loose. Quote Link to post Share on other sites
Ralph Whitaker Posted January 12, 2022 Report Share Posted January 12, 2022 18 hours ago, boxofbits said: Thread drift? ..yeah nice one Rob ! I’d argue that a spring washer might exert a few ounces of clamping force even when flattened as it will distort to some extent. A shakeproof has small teeth as you know but once flattened might not even exert any pressure at all. I’ve not known many spring washers to fail in practice though. My car would be in bits all over the driveway by now if that was the case! The person doing the tightening didn’t seem to be putting much elbow into it, and did I see a dodgy cheapo Halfords socket being used? Not surprised it came loose. +1 for above comments. I have often seen a spring washer shave off metal either from the nut or the object being fastened. Only thing I would say is that you often see them used in conjunction with a flat washer which negates the effect of the spring washer somewhat as the nut/spring washer/flat washer can then all turn together. Ralph Quote Link to post Share on other sites
Lebro Posted January 12, 2022 Report Share Posted January 12, 2022 2 hours ago, Ralph Whitaker said: Only thing I would say is that you often see them used in conjunction with a flat washer which negates the effect of the spring washer somewhat as the nut/spring washer/flat washer can then all turn together. Ralph Yes, I have often wondered about the wisdom of fitting a flat washer under a spring one. Bob Quote Link to post Share on other sites
boxofbits Posted January 12, 2022 Author Report Share Posted January 12, 2022 5 hours ago, Ralph Whitaker said: +1 for above comments. I have often seen a spring washer shave off metal either from the nut or the object being fastened. Only thing I would say is that you often see them used in conjunction with a flat washer which negates the effect of the spring washer somewhat as the nut/spring washer/flat washer can then all turn together. Ralph 2 hours ago, Lebro said: Yes, I have often wondered about the wisdom of fitting a flat washer under a spring one. Bob Agree with those remarks. I’ve noticed some flat washers integral to the nut have a serrated flat, usually metric, but I’ve not seen this on an individual steel flat washer. I was always taught flat washer, spring washer, and nut, though there’s always a possibility of a flat turning on its surface. Without checking again, I think the manual for this part only shows a spring and nut. On a prop shaft for instance it’s usually bolt and nyloc, with no washer. Generally speaking though, unless a spring washer snaps, which I’ve seen, the conventional set-ups are usually reliable. Kevin Quote Link to post Share on other sites
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